Toner for electrophotography

ABSTRACT

A POSITIVE CHARGEABLE TONER FOR ELECTROPHOTOGRAPHY IS PRPARED BY DISPERSING A COLORING AGENT AND A CHELATE COMPOUND OF ETHYLENE DIAMINE TETRAACETIC ACID AND A METAL OF BI-, TRI OR TETRAVALENCE, INTO A BINDING RESIN.

United States Patent Office 3,826,747v Patented July 30, 1974 US. Cl. 252-621 5 Claims ABSTRACT OF THE DISCLOSURE A positive chargeable toner for electrophotography is prepared by dispersing a coloring agent and a chelate compound of ethylene diamine tetraacetic acid and a metal of bi-, trior tetravalence, into a binding resin.

BACKGROUND OF THE INVENTION Field of the invention The invention of the present application relates to a positively chargeable toner used for development of electric image in a process of electrophotography or a process of electrostatic recording.

Description of the prior art A process of electrophotography was disclosed in US. Pat. No. 2,297,691, Japanese Patent Publication No. 23,910/ 1967, Japanese Patent Publication No. 24,748/ 1968 and the like, in which an electric image is formed on a photosensitive member by utilizing a photoconductive material, forming a latent image thereon, developing with a toner, transferring the resulting toner image to a paper, and thereafter fixing by heating or solvent vapor to obtain a copy.

As methods for visualizing electric images by using a toner, there are well known a magnetic brushing method mentioned in the US. Pat. No. 2,874,063, a cascade developing method mentioned in the US. Pat. No. 2,618,552, a powder cloud method mentioned in the US. Pat. No. 2,221,776 and the like. In addition to the above mentioned dry type developing method, a liquid developing method using a developing solution which is prepared by dispersing particles of toner into an insulating liquid such as isoparallin is known.

The toner used for the above mentioned developing method is positively chargeable or negatively chargeable, which is used properly at need.

Hitherto, chargeability of the toner has been controlled with a binding resin, a dye and the like. Accordingly, when positively chargeable toner is prepared, combination of a binding resin and a dye or pigment is limited, and consequently it has been difficult to obtain a toner satisfying all of fixability, chargeability, colorability, stability during storage and the like. Particularly, in the toner for coloring since selecting of a binding resin is difiicult on account of limiting of a kind of dye used, it is difficult to obtain a satisfactory positively chargeable toner by only combination of a binding resin and a dye.

Hitherto, in case of a black toner, when satisfactory positive chargeability can not be obtained by adding carbon black to a binding resin, a gilsonite has been added to control positive chargeability. Since the gilsonite is natural resin so that it is suffered from fluctuation of quality among lots and further it is black, it has not been used for the color toner at all.

In case of a liquid developer, a toner is sometimes coated with a charge controlling agent, such as resinous materials but it is preferable that the toner itself has strong positive chargeability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a positively chargeable toner which is free from usual faults as mentioned above and is not limited by a binding resin and coloring agent.

Another object of the present invention is to provide particularly preferable positively chargeable toner using for coloring electrophotographic method.

A further object is to provide a positively chargeable toner for an electrophotography which comprises dispersing into a binding resin a coloring agent (dye or pigment) and a chelate compound of ethylene diamine tetraacetic acid (EDTA) and a metal of bis-, trior tetravalence represented by the following formula:

MOOCCH; CHQCOOM NCHJCHIN MOOCCH; CHiCOOM wherein M is, similar or dissimilar, hydrogen, alkali metal or NH DESCRIPTION OF THE PREFERRED EMBODIMENT In the present invention, the strong positive chargeability of the toner is controlled by adding a chelate compound of the above mentioned ethylene diamine tetraacetate and a metal free from limitation of a binding resin and a coloring agent (dye or pigment), and a metal chelate compounds used in the present invention are shown in Table 1.

TABLE 1 Ghelate compounds N aAlY N azBaY N aBiY NBZCQY NazCdY NaCeY N EQCOY N aCrY NazCluy NaDyY NaEuY N aFeY NH4 GaY NazGeY HfY NazHg Y N aInY N aLaY NazMgY NazMnY NaMnY N84(M00a)zY N aNdY NaaNiY NazPbY HzPdY HzPtY 4[ B20 2( )2l iii iiiii) Y 11 2 NazSbY Contained water In Table 1, Na may be replaced by K, NH, or Li and Y represents "COUCH; CHgCOO N.CH:.CH2.N

'OOC.CH2 CHQCOO" The above mentioned metal chelate compounds are all useful for the present invention, but white compounds are preferable for coloring electrophotography. Metals used may be those of di-, trior tetravalence capable of forming a metal chelate with ethylene diamine tetraacetate.

The amount of a metal chelate in the present invention is 1-15% by weight, preferably 2-8% by weight. The amount of 1% or below does not give a large effect of controlling positive chargeability and is not preferable. The amount of over 15% does not increase the effect of controlling chargeability and is not preferable for fixability and stability during storage.

As the binding resin used for the toner of the present invention, resins used for usual toner may be used, in which polystyrene, polyester, epoxy resin, acryl resins, styrene-maleic acid copolymer, hydrocarbons having high softening point, polyethylene, polyvinyl chloride, maleic acid resin, phenalic resin and the like are particularly preferable.

As the coloring agent, dyes and pigments used for usual electrophotography may be used. For example, Carbon Black, Orasol Brilliant Blue, Orasol Red, Orasol Yellow, Oil Yellow, Neozapan Blue, Lumogen Yellow, Microlich Blue and the like are used.

The toner of the present invention is used for various developing method. Said toner is mixed with iron powder, for or glass beads as a carrier in the case of using for a dry type developenand is dispersed into higher insulating liquid in the-case of using for wet type developer. Said higher insulating liquid may be that used for a usual developer. For example, aromatic hydrocarbon, paraffin series hydrocarbon and the like having volume resistivity of higher than ,10 ohm.cm. and dielectric constant of less than 3 are used.

A dispersing agent, a fixing agent and the like may be added to the toner.

The toner has strong positive chargeability, and may be obtained by preparing the toner composition of the present invention .as described above.

The following examples are given for illustrating the present invention, but should not be construed as limitation thereto.

EXAMPLE 1 Parts Polystyrene (trade name: Piccolastic D-125, manufactured by Esso Co.) 50 Carbon black 6 EDTA metal chelate (Na BaY.2H 15 The above materials were mixed and melted in a roll mill, and after cooling, said mixture was ground by a jet mill grinder. Said ground powders were sieved to obtain the toner of 30 microns in size.

Example number Binding resins 2 Polystyrene rln Parts Coloring agents Said toner was mixed with iron powders having particle size of 200-600 mesh to obtain dry type developer. The toner content is 5-20% by weight, and preferably about 10%.

The image was formed by an electrophotographic copying machine (trade name: NP-ll00, manufactured by Canon Co.) with said dry type developer, and there can be obtained from a positive original a clear negative image which has high image density and does not have image tailing, and the back ground is free from fog.

Furthermore, toners prepared by using polyester resin, epoxy resin, polyvinyl chloride in place of polystyrene resin were used as a dry type developer, and the same results as above were obtained. I

The following Table 2 shows amounts of charge of various toners of the present invention.

The toners tested were prepared according to Example 1.

The amount of charge was measured as follows: about 5 parts by weight of a sample of the toner was mixed with about 95 parts of reduced iron powder of 250-350 mesh, and said mixture was put in a metallic sieve of 400 mesh. The sieve was placed on a completely insulated stand and its frame was connected with a condenser. The toner adhered to the iron powder was sucked and separated through the sieve by sucking from the bottom of the sieve. The iron powder could not pass through the sieve and remained in the sieve, and was electrized in the opposite charge to the toner. Said charge of iron powder was remained in the condenser. The relation between electric potential of the condenser (V) and an amount of charge per 1 g. of the toner (Q) is as follows:

wherein m is an amount g.) of the toner, C is a capacity (,uf.) of the condenser.

EXAMPLE 2-50 Dry type developers were prepared following the procedure of Example 1 by using the following composition.

TABLE 3 Parts Carbon black 50 Orasol brilliant blue... 50 Carbon blaek-- 50 do- 50 Orasol redremeewwoaw-ooorenwonewmoiuuvhcaemhoaomooeewcn 50 o 50 Orasol yellow 50 Neothapon blue 28 Carbon black 50 Orasol brilliant red 50 Orasol brilliant blue... 28 (Jargon black- TABLE 3-Continued Example number Binding resins Parts Coloring agents Parts EDTA metal chelates Parts Styr ene-aorylie ester copolymer.

48 -do 9 Polyethy e ri n NaCeY NHiGaY 2.

MB ay 41120 1 Trade name: Neopolymer 140.

Then, a positive original was exposed on a ZnO paper electrized to 6 kv. and was developed with said each developer to obtain each fogless and clear positive image.

When EDTA metal chelates were not added, the obtained images were all foggy and not clear.

The following Table 3 shows maximum image density and fog density in case of no addition of EDTA metal chelates (A) and in case of addition of the same amount of gilsonite as that of EDTA metal chelates in place of EDTA metal chelates (B) in Example 2.

The above three materials were mixed and melted. The mixture was cooled and then crushed. To a portion of the crushed powder, parts of Isoper-H (trade name) was added, mixed and ground by a ball mill to a particle size of 1 micron. 10 parts of said liquid was dispersed into 200 parts of isoparafiin solvent (trade name, Isopar H) to obtain a wet type developer.

Then, a positive original was adhered to a ZnO photosensitive paper charged with negative corona discharge at 5 kv., was exposed in light of 800 lux/sec. and was developed in said developer to obtain a fogless and clear positive image.

The above test was made by using each of EDTA- Metal Chelates of No. 2-No. 42 in Table 1 in place of NaAly, and the results were all the same as that of Example 51.

The following Table 5 shows an effect of the toner of the present invention.

(Measuring method).

The developing solution containing 0.5% of the toner (particle size of 1-2 microns) is closed in a transparent tube of diameter of 1.5-1.7 cm. having a silver electrode on both sides. Electric pressure of 500 v. is applied to both sides of the tube, and a positively charged toner migrates in a carrier solution and adheres to the cathode. Charging polarity of the toner is judged by the amount of the toner adhering to the anode or cathode.

EXAMPLE 52 A color original was exposed through a red filter on a panchromatic sensitized ZnO photoconductive layer which was uniformly electrized by charging with corona discharge at -6 kv., and the resulting negative electrostatic image was developed with the developer of Example 19. The developed image was transferred to a copying paper, heated and fixed. The above image was again exposed through a green filter on the ZnO photoconductivei layer electrized in a way similar to the above mentioned procedure, and the resulting negative electrostatic image was developed with the developer of Example 18. The developed image was transferred to a copying paper and fixed. The above image was continuously exposed through a blue filter on the ZnO photoconductive layer electrized in a way similar to the above mentioned procedure, and the resulting negative electrostatic image was developed by the developer of Example 17. The developed image was transferred to a copying paper and fixed to obtain a fogless and clear coloring copy.

We claim:

1. In a finely divided toner for electrophotography containing a binding resin and a coloring agent selectedfrom the group consisting of dyes and pigments, both adapted for electrophotography and both adapted to be admixed or dispersed with a carrier during development, the improvement which comprises an additive for said toner comprising a metallic chelate compound of ethylene diamine tetraacetic acid or derivatives thereof of the following formula CHgCOOM GHaCOOM wherein M represents, similar or dissimilar, hydrogen, alkali metal and NH;, and a metal of bi-, trior tetravalence, said chelate providing enhanced positive chargeability, said chelate present in amounts from about one to 15% by weight based on the total weight of said toner.

2. The toner for electrophotography according to claim 1 in which the metal of bi-, trior tetravalence forming the metallic chelate is Al, Ba, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Eu, Fe, Ga, Ge, Hf, Hg, In, la, Mg, Mn, Mo, Nd, Ni, Pb, Pd, Pt, Re, Rh, R-u, Sb, Sm, Sn, Sr. Ti, Th, U, V, W, Y, Zn, or Zr.

3. The toner for electrophotography according to claim 1 which contains 28% by weight of the metallic chelate compound.

4. The toner for electrophotography according to claim wherein M represents hydrogen, alkali metal, or NH B 1 in which the metallic chelate compound is represented represents a divalent metal; Yrepresents by the following general formula: CHZCOO- N-CH2CH2N wherein M represents hydrogen, alkali metal or NH.;; A 5 -OOC-CH= CHZCOO represents a trivalent metal; Y represents References Cited "OOC-CHz CHzOOO" 3 674 736 2 1??? EATES PAITENTS 252 62 1 10 rman et a CHCOO 3,595,662 7/1971 Willems et al. 96109 R 5. The toner for electrophotography accordlng to claim 0 92 9 19 2 Fairbanks et 1 96 94 1 whereinthe metallic chelate compound is represented 1 by the following general formula: RONALD H. SMITH, Primary Examiner M BY 15 J. P. BRAMMER Assistant Examiner 

